Unlike Microsoft, Google reduces its carbon emissions through the use of carbon credit offsets -- investing in an activity that reduces carbon emissions elsewhere when renewable energy isn't available. The carbon credit is verified by a third party, and it signifies that greenhouse gas emissions are lower than they would have been had no one invested in the offset. One credit equals one metric ton of carbon dioxide prevented from entering the atmosphere, according to Google. For example, if a Google data center is located in a region without renewable energy, Google would invest in renewable energy in another region that may not even effect its facilities directly.
"The deals we enter into, you can be assured we've done internal analytics to ensure it meets our cost thresholds," Demasi said.
The U.S. military's efforts
Along with large corporations, the U.S. military is turning out to be one of the largest deployers of renewable energy. Last month, the U.S. Army installed its largest solar power farm to date at the White Sands Missile Range in New Mexico. The solar array, which cost $16.8 million, is a 4.46 megawatt ground-mounted system comprised of Solaria solar modules that were deployed by Siemens. The White Sands Missile Range solar energy system will take up two acres of land and will generate approximately 10 million kilowatt-hours of clean electricity annually. That's enough to save an estimated $930,000 a year.
Complemented by a 375-kilowatt solar carport for employees, the solar array at White Sands will supply approximately 10 percent of the total power used at the installation and reduce carbon emissions by 7,400 tons per year.
"When talking hundreds of megawatts, you're talking about covering quite a bit of space," said SEIA's Hitt.
Aided by tax incentives, the increase in solar deployments can be attributed to a sharp drop in installed system prices. Solar efforts are getting cheaper for two reasons: an improvement in silicon wafer production and economies of scale.
Photovoltaic power technology advances
SEIA's Shugar, who is also CEO of solar voltaic installer Solaria Corp., said the technology to make the crystalline silicon wafers used for photovoltaic cells has improved exponentially over the past few decades. The silicon wafering process begins with solid ingots made of single-crystal or multi-crystalline silicon material. Thirty years ago, blocks of silicon ingots were sliced into thin wafers by hand using expensive and inefficient diamond saws, much in the same way a butcher slices cold cuts. The relatively thick wafers were then used to make photovoltaic cells.
In the 1980s, the solar industry began using wire saws to cut the ingots into wafers. Each slice was 500 microns in thickness (a micron is 1/1,000 of a meter). Historically, every five years, silicon wafer production has seen a 50-micron reduction in thickness. Today, wire saws slice an entire block into wafers at the same time, each wafer being only 150 microns in thickness, Shugar said.
Because of cost reductions, Shugar said solar deployments have grown by 50 percent to 100 percent every year for the past 12 years.
"It really is a technology story at the end of the day," Shugar said.